OLED displays, that is, organic electroluminescent displays, have become more and more widely used due to their advantages of light emission, wide viewing angle, almost infinitely high contrast, low power consumption, and extremely high reaction speed. The luminous efficiency of OLED displays is a key parameter to evaluate the display performance. The higher the luminous efficiency, the more efficient the conversion of electric energy into light energy at a certain electric power, which is helpful to save power and improve the hour life of the OLED panel. The luminous efficiency of the OLED panel is related to the quantum efficiency and the light extraction rate in the OLED panel, and as a key parameter affecting the intrinsic luminescence, it is very important to improve the quantum efficiency in the luminescent layer. To improve the internal quantum efficiency of the light-emitting layer from the OLED manufacturing materials, light-emitting layer epitaxial growth process and OLED light-emitting layer of light on the way to be studied.
OLED luminescence technology is injection type luminescence, under forward voltage driving, the anode injects holes into the light-emitting layer (EML), the cathode injects electrons into the light-emitting layer, the injected holes and electrons meet in the luminescent layer to combine into excitons and excitons to recombine and transfer the energy to the luminescent material, which emits light after the radiation relaxation process. However, not every pair of electrons and holes will generate photons. Due to the material quality, dislocation factors and process defects in the light-emitting layer of the OLED panel, problems such as impurity ionization, excitation scattering, and lattice scattering arise. The electron transition from the excited state to the ground state and the lattice atoms or ion-exchange energy occurs when there is no radiation transition, that is, does not produce photons, this part of the energy is not converted into light and converted into heat energy loss in the light-emitting layer, so there is a composite carrier conversion efficiency, that is, Nint=(compound carriers generated photons/total number of composite carriers)×100%, called the OLED panel luminous internal quantum efficiency.
In the existing OLED structure, the hole transport layer (HIL) prevents the migration of free electrons, the light-emitting layer hinders the migration of holes. However, some holes enter the light-emitting layer through the blocking layer between the hole transport layer and the light-emitting layer, resulting in the blocking layer becoming a main region where electrons and holes recombine into excitons, that is, an area that emits light effectively. However, since the blocking layer is limited, and the blocking layer is an interlayer interface similar to the “wall” to prevent electrons from entering the hole transport layer, to some extent to prevent holes into the light-emitting layer, inevitably form a “rebound” of electrons and holes.